• Changbin Du's avatar
    perf ftrace: Append an EOL when write tracing files · 63cd02d8
    Changbin Du authored
    Before this change, the '--graph-funcs', '--nograph-funcs' and
    '--trace-funcs' options didn't work as expected when the <func> doesn't
    exist. Because the kernel side hid possible errors.
    
      $ sudo ./perf ftrace -a --graph-depth 1 --graph-funcs abcdefg
       0)   0.140 us    |  rcu_all_qs();
       3)   0.304 us    |  mutex_unlock();
       0)   0.153 us    |  find_vma();
       3)   0.088 us    |  __fsnotify_parent();
       0)   6.145 us    |  handle_mm_fault();
       3)   0.089 us    |  fsnotify();
       3)   0.161 us    |  __sb_end_write();
       3)   0.710 us    |  SyS_close();
       3)   7.848 us    |  exit_to_usermode_loop();
    
    On the example above, I specified the function filter 'abcdefg' but all
    functions are enabled. The expected result is for all functions to be
    filtered, since there is no such function ('abcdefg')
    
    The original fix is to make the kernel support '\0' as end of string:
    https://lkml.org/lkml/2018/1/16/116
    
    But above fix cannot be compatible with old kernels. Then Namhyung Kim
    suggest adding a space after function name.
    
    This patch will append an '\n' when write tracing file. After this fix,
    the perf will report correct error state. Also let it print an error if
    reset_tracing_files() fails.
    
    Committer testing:
    
    Now it prints:
    
      # perf ftrace -a --graph-depth 1 --graph-funcs abcdefg
      failed to set tracing filters
      #
    
    And for an existing function:
    
      # perf ftrace -a --graph-depth 1 --graph-funcs SyS_open
       3)               |  SyS_open() {
       3) ! 494.899 us  |  }
       0) + 23.910 us   |  SyS_open();
       1) + 17.115 us   |  SyS_open();
       1) + 13.900 us   |  SyS_open();
       ------------------------------------------
       3)  qemu-sy-2817  =>  pickup-1290
       ------------------------------------------
    
       3) + 20.021 us   |  SyS_open();
      #
    Signed-off-by: default avatarChangbin Du <changbin.du@intel.com>
    Tested-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
    Cc: Jiri Olsa <jolsa@redhat.com>
    Cc: Namhyung Kim <namhyung@kernel.org>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Link: http://lkml.kernel.org/r/1519007609-14551-1-git-send-email-changbin.du@intel.comSigned-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
    63cd02d8